Help needed wiring up reworked Explorer harness into the stock wiring harness. Thank you

[76Bronko]

Hello everyone, first post here. My bronco is a 76 and I am doing an Explorer swap using the 4R70W and the NP205, and am keeping all of the EGR stuff. I have had my PATS deleted locally, and have had my donor Explorer wiring harness reworked by EFI guy. (Awesome harness, by the way, Garry) Electrical isn't one of my strong suites, and the wiring diagrams that I've found online aren't the clearest, so I'm just going to ask for some help. Does anyone have any directions as to how (and where) to wire my reworked Explorer harness into my stock harness? Pictures would be super helpful. Some of the main questions I'm having are things like I have no clue what the ring connectors ends (marked coolant temp and oil pressure gauges) are supposed to hook up to on the Explorer intake, since I have a ECT sensor......the wire that's marked + battery is a much smaller gauge than what I'm used to seeing for battery terminals..... am I just supposed to splice on a larger gauge wire to that wire and run that to the battery?

Any help is appreciated, I'm four years in and would be close to starting the Bronco for the first time that I've owned it, once the wiring harnesses (stock and reworked Explorer) are playing nice with each other.
Thank you!

 

[widowmaker77]

So are you saying the wires for the gauge cluster is in the explorer harness? I’m running 99 explorer efi. I also have the centech harness that has all the wires for my gauge cluster in it. My son did my harness from Gary’s videos he put out a few years back. As far as the ring terminals go for coolant temp and oil pressure gauge go, it’s just basic round ring terminals that will slide over the threaded posts on a 77 style coolant and oil pressure sensor then find a machine screw that will thread on the post. I can’t remember what the thread pitch is.
The smaller hot wire can probably just be ran to the hot post on the fender mounted solenoid switch. That’s what I did for a few things like that BUT I deleted my egr stuff. I can get a couple of pics tomorrow when I get back to my rig, if you still need them?

 

[76Bronko]

Thank you for the reply. The reworked wiring harness has both a ECT sensor original to the Explorer intake, and two ring terminals, one marked coolant temp and the other marked oil pressure, which has confused me. So it's sounding like to get my gauges to work, I'll have to drill and tap my Explorer intake and put in an early bronco engine oil sensor and a coolant temp sensor, then connect the ring terminals to the sensors. That's kind of a bummer, I was hoping the reworked harness would have something coming from the ECM that would work my gauges.....Pictures would be helpful, absolutely. Take your time, I'm going nowhere fast with this electrical stuff lol. Before I take a stab at it, I'm going to listen to all the help I can.

Thanks, Mel

 

[widowmaker77]

Thank you for the reply. The reworked wiring harness has both a ECT sensor original to the Explorer intake, and two ring terminals, one marked coolant temp and the other marked oil pressure, which has confused me. So it's sounding like to get my gauges to work, I'll have to drill and tap my Explorer intake and put in an early bronco engine oil sensor and a coolant temp sensor, then connect the ring terminals to the sensors. That's kind of a bummer, I was hoping the reworked harness would have something coming from the ECM that would work my gauges.....Pictures would be helpful, absolutely. Take your time, I'm going nowhere fast with this electrical stuff lol. Before I take a stab at it, I'm going to listen to all the help I can.

Thanks, Mel

I’ll try to get some pics tomorrow but the coolant temp sensor for gauge screws into the lower intake on the driver side. The oil pressure sending unit screws into the block right above the oil filter on the driver side. No drilling is needed for either

 

[widowmaker77]

I found this pic of my engine during install and zoomed in. Where the paper towel is in the intake between the bolt and fuel rail, is where my coolant temp fir the gauge is.

 

[dmoses42]

Been a while since I watched the videos Garry put out on reworking the harness, but I'm pretty sure the ECT sensor is used for/by the computer, and the coolant temp ring terminal is for your gauge cluster. There should be a location on the intake to put a temp sender that would be factory for the Bronco, close to where that ring terminal is. The oil sender (also for your gauge cluster) will be on the block down near where the mechanical fuel pump would have been. Just take out the one for the Explorer and put one in that is for the Bronco. If you have time, watch those videos (there's three). They are long and dry, but they will answer where all your wires go. Check out this thread:

https://classicbroncos.com/forums/threads/explorer-obd2-harness-re-work.257251/

And these videos:

 

[Bruners4]

I'm running one of EFI Guy's reworked harnesses and can lend a little assistance. I have EGR and EVP delete. I have two engine temp sensors, the Explorer ECT screwed into the stock location as above close to the valve cover and the Bronco Temperature gauge in a T-fitting on the heater hose line by the coolant thermostat housing. I also have two oil pressure sensors, the Explorer sensor for the ECU and the Bronco Oil Pressure gauge. Oil pressure sensors are on the drivers side of the engine block above the oil filter.

 

[76Bronko]

Thank you all so much. It is very gracious of you all to reply. I will order stock early bronco temperature and oil pressure sensors and try to nail down where to put them using your pictures. and locations. Also will I be using a stock early bronco fender mounted solenoid, or will the starter relay with the reworked EFI guy harness hot wire go directly to the solenoid attached to the Explorer starter? I should have asked for help awhile ago. Thanks everyone

 

[widowmaker77]

So just to clarify my setup a little bit, my temp sensor for the gauge is screwed into the manifold like I said above. My ect sensor for the ecm is screwed in the coolant crossover pipe just like oem. If you don’t have the crossover pipe, wherever you put your ect sensor , it needs to be located where water continually passes by it. Thats why the crossover pipes have the little tube welded between the two behind the ect sensor. This keeps the water in the heater hoses from deadheading and giving the ecm a false temp reading.

 

[904Bronco]

So just to clarify my setup a little bit, my temp sensor for the gauge is screwed into the manifold like I said above. My ect sensor for the ecm is screwed in the coolant crossover pipe just like oem. If you don’t have the crossover pipe, wherever you put your ect sensor , it needs to be located where water continually passes by it. Thats why the crossover pipes have the little tube welded between the two behind the ect sensor. This keeps the water in the heater hoses from deadheading and giving the ecm a false temp reading.

Question... Below is what Garry has used in the past for a fuse box, Is this the same as you have? If so, is this the size red wire you are asking if you need to hook to the Batt? If it is, then you would hook it to the Batt side of the Starter relay if you are running the factory Explorer PM starter. (My 71 Bronco has a Centech harness)
What everyone is saying above is correct, that Garry's harness will have a plug for the ECT, which is typically placed in the Explorer coolant tubes (they have the bypass as described). What I think Garry did, was to include the (extra) Coolant temp and oil pressure wires (red/white and green/white?) from the Explorer harness for you. You don't have to use them, if your existing harness to these sensors is still in service. You will have to use the Bronco sensors so your gauge cluster works correctly. Be careful screwing the temp sensor into the port on the drivers side front of the lower intake. I have cracked the intake by screwing it in too far. More than likely, you will need to use the bronco oil pressure sensor extension pipe for the oil sending unit. I believe the studs on both sensors are a 8-32" thread...

 

[widowmaker77]

Thank you all so much. It is very gracious of you all to reply. I will order stock early bronco temperature and oil pressure sensors and try to nail down where to put them using your pictures. and locations. Also will I be using a stock early bronco fender mounted solenoid, or will the starter relay with the reworked EFI guy harness hot wire go directly to the solenoid attached to the Explorer starter? I should have asked for help awhile ago. Thanks everyone

I’m pretty sure you will have to run the fender mounted solenoid. Also make sure you have very good grounds. I drilled and tapped my frame in three different places one ground to the block, one to the tub and then my battery ground I used ground straps from Tom’s and stainless bolts then I covered them in liquid tape. So far I haven’t had any type of ground issues. If you painted or powder coated your front dress brackets, then you will need to run a designated ground wire to the alternator housing. I smoked my first explorer alternator because I had painted my brackets and the alt wasn’t grounded.

 

[76Bronko]

Thank you!

 

[EFI Guy]

No matter which style of fusebox you have it should be mounted somewhere near the fender-mounted solenoid and your power feed should connect to the battery side of the solenoid. This is as close you can get to connecting straight to the battery without having to worry about the corrosion seeping into the harness.

The 2 wire ECT is for the computer and mounted in the heater tubes. The single wire (red/white) is for the gauge but must be used with the Bronco sender. If it has a ring terminal it's because I cut the Explorer connector off. I can't remember the nut size needed, I think it's something like a 6-32 or 8-32. This sensor mounts near injector #5

There is no oil pressure input to the PCM. Just a single wire for the gauge only.

 

[76Bronko]

Thanks everyone. Just got the early bronco oil and temp sensors from Bronco Graveyard. Will be putting them in and wiring them up shortly. Help was very much appreciated. Mel

 

[76Bronko]

Next questions, to anyone who can help......

The oil pressure and coolant temperature senders are installed. And with the basic wiring diagrams that I have found, I know where/how to wire them up. But that's only two out of 14 wires that go to the dashboard/firewall area that I have to figure out, so more questions......

These wires are what I think are the more important ones, so I thought I'd start there....

1) From reworked explorer harness. Pink wire labeled 'Ignition switch start signal. Hot in start only'. Connect this to the red and blue wire 32 in the wiring diagrams, in parallel, so that other legs of the wire run to the ignition switch itself and to the solenoid "S" terminal?

2) From reworked explorer harness. Red wire labeled 'Ignition run switch. Hot in run and start.' Is the only wire that is hot in run and start the wire that would normally go to the coil? Connect this to the red and green wire, and let it terminate at the ignition switch, because I have no coil?

3) How does my 4G explorer alternator wiring work? I am only seeing a connector that hooks to the voltage regulator at the actual alternator. There is no large diameter wire to go to the alternator to my battery located on the reworked Explorer wiring harness

4) For the explorer swap with the reworked harness, I don't use any of the early bronco voltage regulator or the ignition control module at all, do I?

5) For all of the accessories from the reworked explorer harness that need 'hot in run' should I use wire 904, the Red and Green wire? and if so, (ignition run switch, alt warning light bulb, check engine light bulb, reverse light switch input) do I just splice into the 904 wire at one place and run all 5-6 wires from that splice to those accessories?

Pictures are very, very, much appreciated. If there is a link to something in here already, I apologize for not finding it. You have all been great. Hope to hear from you!

 

[DirtDonk]

3) How does my 4G explorer alternator wiring work? I am only seeing a connector that hooks to the voltage regulator at the actual alternator. There is no large diameter wire to go to the alternator to my battery located on the reworked Explorer wiring harness

Nobody is going to include a main BAT charge wire that I can imagine. It's not part of the engine harness, per sé and is going to be strictly "per vehicle owner specifications" and will vary greatly on how the engine compartment is set up.
My own is a good example. The battery is moved over to the driver's side due to the reworked intake system and filter. So alternator charge and battery cables are quite a bit different from one that is still in the original location.
Wire gauge requirements could be anywhere from 8ga to 2ga, depending upon your needs and desires. In lengths from maybe 12" to 60" and a fuse holder, or fusible link put somewhere in the system.
In other words, it's up to you.
You can source a stock charge cable setup from the junkyard (you have a full Explorer, or just the engine?), or you can buy a pre-made kit from someone like us at Wild Horses. As long as what is available will work with your setup. Or you can make your own, or have one made to your needs.
Fuse type and rating would depend on if you have a stock alternator, or some high-falootin wazoo 400 amp model.
Show us a pic of your engine compartment and maybe some more suggestions will be forthcoming.

4) For the explorer swap with the reworked harness, I don't use any of the early bronco voltage regulator or the ignition control module at all, do I?

Maybe, maybe not...
Stock original '76 wiring, correct? You might need the Green w/red stripe wire for your new alternator, if it's matching wire in the new harness is not connected to anything.
Or maybe Garry has enough wire to run the new harness all the way to the ignition switch?
Either way, the alternator regulator Green w/red wire also needs a hot-in-run-and-start power source. Maybe the Red w/green wire that you mentioned before?
Might be one of those 14 other wires then. You still need a "key ON only" wire to get power to the Green w/red wire at the new alternator connector. Your original one was over on the passenger firewall? Or was it over on the wheel well or fender apron? Either way, you may need to re-use it for your new internal regulator.
Same for the original Yellow wire from the old regulator. That might need to be connected to the new Yellow w/white wire at the new alternator regulator harness.

ICM? Are you running all Explorer engine stuff with fuel injection and computer controlled ignition? Sounds like it, so I'll just answer as if that's the case.
If so, and you're letting the EFI computer control the ignition like it would on an Explorer, then no, you don't need ANY of the old ignition wires or ignition control module.
But don't cut them and toss them out just yet! You might be able/need to repurpose one or some of them for their new duties.

Sorry if you have gone over this already, but are you going to use the Explorer coil packs? Or are you converting to a distributor and working with a non-Explorer computer?
Sorry too, for jumping in and adding more questions when someone like EFI Guy or 904Bronco could probably just tell you where to put each of your wires. But I thought I'd at least add my 2 cents worth on the charge cable, and start the discussion about the others.

Paul

 

[904Bronco]

3)
Buy the Batt fused Alt kit from Wild Horses. Or you can make your own...
Use the Green/red-stripe wire from your original harness for the field wire on the G4
Yellow Batt sensing wire to the back of the Alt Batt terminal
Depending on the Alt Plug, (see below) you do not use the white/black stripe wire (stator) on this application

 

[904Bronco]

1)
Looking for a start signal... connects to the red/blue stripe wire that goes to the Starter relay on the fender.

4)
No you would not be using any of the Voltage regular or Ignition wires.
But need the Green red stripe field wire at the regulator for the G4 and it has been a while but, one of the Ignition wires to your ignition box may have the run start signal wire signal you need... Test light and voltage meter will help with that.

 

[EFI Guy]

1. Connect to the ignition switch or to the red-blue just after the ignition switch. You can remove the remainder of that circuit from your harness, the Explorer harness handles your NSS.

2. Connect to the ignition switch or to the red-green just after the ignition switch. If you have resistor wire this must connect before the resistor so that the EFI gets a full 12v.

3. If you have a later harness where the ALT plug is present then you only need to add the charge post wiring. Use 6awg and a 175a megafuse. If you have an early harness without the ALT plug then follow Doug's directions above.

4. No. The Explorer alternator is internally regulated.

5. You can. But I would keep the coil wire to trigger the EFI only. That way any sort of short from anything else on that circuit won't leave you stranded. I believe Painless #914 (green/red) is a better choice to provide power to your lights and switches (except reverse lights). If your harness has the ALT plug then the green/red coming in under the dash connects to #914, optionally you can wire in a warning light between the two.

My documentation shows Painless #956 for reverse lights.